A newly discovered species of orange-coloured mould has been named after soon-to-be Dutch king Willem-Alexander and his family, the scientists behind the move said Friday.

The mould was named after the Prince of Orange, the title given to the Dutch crown prince, "because what distinguishes this is its orange colour, a very rare phenomenon," Pedro Crous, head of the Dutch CBS-KNAW fungal research centre said in a statement.

One mould has been called penicillium vanoranjei ('of orange' in , in reference to the royal house of Orange-Nassau) and one P.maximae, after his Argentine-born wife Maxima.

The other three are named P. amaliae, P. alexiae and P. arianeae after the couple's three young daughters.

Queen Beatrix, 75, is to abdicate in favour of Willem-Alexander, 45, in Amsterdam on April 30.

Scientists have not yet worked out whether the new will serve any useful medical purpose.